The present invention relates to a novel SSB (single sideband) radio receiver. More particularly, the present invention relates to a SSB radio receiver which is intended to reduce the cost of production of such SSB radio receivers, by avoiding the use of an expensive band-pass filter associated with and utilized in prior art SSB radio receivers. Specifically, the present invention negates the need for the usage of expensive band-pass filters which only have a narrowband characteristic to pass only a specific SSB signal.
Generally, an information signal in the form of a typical amplitude-modulated wave has information signals which are contained and distributed uniformly on two sidebands about a central carrier frequency. A system in which these two sidebands are transmitted is called a DSB (double sideband) system. Alternately, a system in which only one of the sidebands is transmitted is called an SSB (single sideband) system. In the SSB system, a required minimum occupied frequency band is transmitted, which results in a higher utilization efficiency in a frequency spectrum, along with higher efficiency in radiation power. Further, the SSB systems have the additional advantages of reducing or eliminating the problems associated with signal interference, signal strength fading, noise and so on.
A SSB radio receiver is used in order to receive an SSB signal. Ordinarily, the typical SSB receiver has a filter such as an intermediate-frequency (IF) filter which allows for the passage of only a single sideband signal that is within the central frequency range of this filter. Usually, a specially designed crystal, ceramic or mechanical filter, having a narrow-band characteristic for passing therethrough only the specified SSB signal, is utilized for this function.
In the typical SSB system, a narrow band-pass filter is utilized for passing the SSB signal, which is in itself very expensive, and its existence in the SSB radio receiver has been an obstacle to a reduction in the production cost of all SSB radio receivers.
In contrast to the prior art SSB receivers, the present novel invention provides a SSB radio receiver in which the expensive narrow-band filter is eliminated and replaced by an inexpensive filtering combination. This inexpensive filtering combination offers the functional equivalent to that of the expensive narrow-band filter, in order for the production cost of the SSB radio receiver to be dramatically reduced. The present invention achieves this novel and practical objective by combining an inexpensive wide-band IF filter with an inexpensive low-pass filter, in conjunction with a SSB detecting stage in the SSB radio receiver, allowing for the reception of a targeted reception objective SSB station IF signal without the use of the prior art expensive narrow-band filter. Other features and advantages of the present invention will become apparent upon a reading of the attached specification.